| In this research,the rhizosphere soils of six salt-tolerant plants,Medicago sativa,Lycium barbarum,Panicum virgatum,Achnatherum splendens,Sophora alopecuroides and Tamarix chinensis,grown in salinized soil in North of Yinchuan District,Ningxia,were used as materials to determine soil physical and chemical properties and enzyme activities by using the national standard method.Biolog ecoplate technology and high-throughput sequencing were used to analyze the bacterial metabolic function diversity and community structure of rhizosphere soil,and then plant rhizosphere growth-promoting bacteria were isolated and screened.By studying the biological characteristics and growth-promoting activities of the strain,the growth-promoting bacteria that grow fast,and have an excellent plant growth-promoting activities and non-antagonistic were chosen and used to construct PGPR microflora.And its growth-promoting effect was verified.The research of this project provides a kind of strain resources for the preparation of eco-fertilizer suitable for the specific climate of our region and can play a stable role in salinized soil.It also provides a solid theoretical basis for the effective use of rhizosphere-promoting bacteria to improve saline-alkali soil.The main contents and results are as follows:(1)Analysis of enzyme activities in rhizosphere soil and metabolic characteristics of microbial communities showed that the physical and chemical properties of rhizosphere soils were different in different plants.Compared with bare ground,six plants could significantly increase soil enzyme activity in saline soils.And the activity of three enzymes in rhizosphere soil of Medicago sativa is significantly higher than other plants.The average well color development rate(AWCD)of soil increased gradually with the prolongation of culture time.The soil microbial community metabolic diversity index was the highest in the rhizosphere soil of Medicago sativa,and followed by that of Achnatherum splendens,which was significantly different from other soils(P<0.05).The carbon source utilization ability of soil microbes in rhizosphere soil of different plants was different.The utilization rate of soil microbes in rhizosphere of Medicago sativa was significantly higher than that of other soils(P<0.05).Carbohydrates were the main carbon source of rhizosphere soil microorganisms.Principal component analysis demonstrated that the main carbon sources that differentiated between PC1 and PC2 were carbohydrates and carboxylic acids.(2)Analysis of rhizosphere bacterial community structure showed that a total of 31 phyla,67 classes,253 families and 400 genera were detected in six soil samples.The bacterial community composition in different plant rhizospheres were similar in different plants,but the relative abundance were different.Firmicutes,Proteobacteria and Actinobacteria were the main dominant groups;At the class level,Bacilli was the highest relative abundance,followed by Alphaproteobacteria,Gammaproteobacteria and Clostridia;at the genus level,Bacillus has an absolute superiority(15.57%-53.85%),followed by Sphingomonas,Acinetobacter,Arthrobacter.The community structure of the rhizosphere bacteria of the six plants showed:That of Achnatherum splendens and Tamarix chinensis were similar;those of Panicum virgatum,Medicago sativa,and Lycium barbarum were similar,and that of Sophora alopecuroides was the most different from the other five plants.(3)110 strains of bacteria were isolated from the six rhizosphere soils,and their growth-promoting ability was screened and identified.The results showed that most of the strains had more than one biological activity and strong salt-tolerance.Among them,11 strains could still grow in the medium containing 15%NaCl,and 54 strains still grew well under the condition of pH 12.0.They were belonging to five genera,Bacillus,Pseudomonas,Sphingobacterium,Arthrobacter,and Sinorhizobium,and with a single diversity at the genus level.Bacillus and Pseudomonas were co-owned genus in the rhizosphere soil of the six plants.(4)Through antagonistic reaction experiments,strains that are not antagonistic to each other were selected used for nine efficient complex microflora constructions.Measurement and evaluation of the promoting function of the nine groups of composite bacteria,C3 and C8 with better growth-promoting ability were screened for back-inoculation experiment.The results showed that the two combinations were highly effective in promoting the growth of Medicago sativa seedlings and Panicum virgatum seedlings.Among them,the C3 was particularly effective in promoting growth.Compared with the control group without PGPR,the height of Medicago sativa and Panicum virgatum were increased by 54.95%and 50.96%,respectively,and the fresh weight on the ground were increased by 113.33%and 125.00%,which had the potential to be developed as microbial compound agents. |
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